1. Field of the Invention
The present invention relates generally to medical methods, systems, and kits. More particularly, the present invention relates to methods and apparatus for the treatment of lung diseases, such as COPD, by creating and controlling atelectasis and hypoxia in segments of lung tissue.
Chronic obstructive pulmonary disease (COPD) is a significant medical problem affecting sixteen million people or about 6% of the U.S. population. Specific diseases in this group include chronic bronchitis, asthmatic bronchitis, and emphysema. While a number of therapeutic interventions are used and have been proposed, none are completely effective, and COPD remains the fourth most common cause of death in the United States. Thus, improved and alternative treatments and therapies would be of significant benefit.
Management of COPD is largely medical and infrequently surgical. Initially, exercise and smoking cessation are encouraged. Medications including bronchodilators and anti-inflammatories are routinely prescribed. Pulmonary rehabilitation has been shown to improve quality of life and sense of well being. Long term oxygen is generally reserved for the more severely affected patients.
Emphysema is a condition of the lung characterized by the abnormal permanent enlargement of the airspaces distal to the terminal bronchiole, accompanied by the destruction of their walls. It is known that emphysema and other pulmonary diseases reduce the ability of part of the lungs to fully expel air during the exhalation phase of the breathing cycle. During breathing, the diseased portion of the lung does not fully recoil due to the diseased lung tissue being less elastic than healthy tissue. Consequently, as the airways normally held open by the elastic pull of the lungs become floppy and the diseased lung tissue exerts a diminished driving force during exhalation, the airways close prematurely resulting in air trapping and hyperinflation.
In addition, hyper-expanded lung tissue occupies more of the pleural space than healthy lung tissue. In most cases, only a part of the lung is diseased while the remaining portion is relatively healthy and therefore still able to efficiently carry out oxygen exchange. By taking up more of the pleural space, the hyper-expanded lung tissue reduces the space available to accommodate the healthy, functioning lung tissue. As a result, the hyper-expanded lung tissue causes inefficient breathing by compressing the adjacent functional airways, alveolar units, and capillaries in relatively healthier lung tissue.
Lung function in patients suffering from some forms of COPD can be improved by reducing the effective lung volume, typically by resecting diseased portions of the lung. Resection of diseased portions of the lungs both promotes expansion of the non-diseased regions of the lung and decreases the portion of inhaled air which goes into the lungs but is unable to transfer oxygen to the blood. Accordingly, recruitment of previously compressed functional airways, alveolar units, and capillaries in relatively healthier lung is possible resulting in more gas exchange in addition to better matching of lung and chest wall dimensions. Lung reduction is conventionally performed in open chest or thoracoscopic procedures where the lung is resected, typically using stapling devices having integral cutting blades.
While effective in many cases, conventional lung volume reduction surgery (LVRS) is significantly traumatic to the patient, even when thoracoscopic procedures are employed. Such procedures often result in the unintentional removal of healthy lung tissue, and frequently leave perforations or other discontinuities in the lung which result in air leakage from the remaining lung. Even technically successful procedures can cause respiratory failure, pneumonia, and death. In addition, many older or compromised patients are not able to be candidates for these procedures.
As an alternative to LVRS, endobronchial volume reduction (EVR) uses endobronchially introduced devices which plug or otherwise isolate a diseased compartment from healthier regions of the lung in order to achieve volume reduction of the diseased compartment. Isolation devices may be implanted in the main airways feeding the diseased region of the lung, and volume reduction takes place via absorption atelectasis after implantation or via collapse by actively suctioning of the target compartment prior to implantation. These implanted isolation devices can be, for example, one-way valves that allow flow in the exhalation direction only or occlusive devices that prevent flow in both directions.
While a significant improvement over LVRS, EVR suffers from a significant risk of pneumothorax. Pneumothorax is a condition which results from air entering the pleural space surrounding the lung. For reasons that are not fully understood, it has been found by the inventors herein that a sudden blockage of a feeding bronchus can create conditions in the isolated lung region which can in some cases cause a pneumothorax. A spontaneous pneumothorax can result from the tearing of pleural adhesions and blebs lying under the visceral pleura of the non-treated lung areas during the rapid development of absorption atelectasis in the treated lung area.
For these reasons, it would be desirable to provide alternative and improved methods and devices for performing endobronchial volume reduction and other lung therapies where the risk of inducing a pneumothorax is reduced or eliminated.
2. Description of the Background Art
U.S. Pat. No. 6,679,264 describes an exemplary flow control element that limits, but does not block, fluid flow in at least one direction. The flow control element comprises a valve member supported by a ring. The valve member is preferably a duckbill-type valve having a similar construction to that of the valve member, except that the flaps are formed, secured, oriented or otherwise configured to maintain a flow opening when in their flow-controlling (as opposed to flow-allowing) orientation. The opening is sized and configured to achieve desired flow characteristics through the flow control element.
U.S. Pat. No. 6,722,360 describes devices and methods for improving breathing in patients with COPD. A mouthpiece is provided, or a device is implanted in the trachea or bronchial passage, to selectively increase flow resistance to expiration while minimally increasing flow resistance to inspiration. The methods and apparatus rely on increasing proximal flow resistance in a manner which mimics “pursed lip” breathing during exhalation which has been found to benefit patients suffering from this disease by keeping the distal airways open for a longer period of time and allowing more of the inspired air volume to be evacuated during the longer exhalation time.
U.S. Pat. No. 7,011,094 describes devices and methods for implanting sealing components within bronchial lumens. The sealing components may include a septum which can be penetrated with a dilation device which can provide a valve or open flow path through the septum.
U.S. 2007/0005083 describes the treatment of diseased lung segments by placing a blocking element in an airway of the lung which leads to the diseased segment.